Phosphine oxide flame retardants

ABSTRACT

Aromatic phosphine oxide compounds are useful as flame retardants in synthetic polymers and textiles. Exemplary is 2,4,5,6-tetrabromo-1,3-xylylenebis(diphenylphosphine oxide).

United States Patent [1 1 Mrowca PHOSPHINE OXIDE FLAME RETARDANTS [75] Inventor: Joseph J. Mrowca, Wilmington, Del.

[73] Assignee: E. l. du Pont de Nemours & Company, Wilmington, Del.

[22] Filed: Nov. 16, 1973 [21] App]. No.: 416,597

[56] References Cited UNITED STATES PATENTS 2,927,945 3/1960 Buckler et a]. 260/606.5 P

[4 1 July 15,1975

3,213,057 10/1965 Ritt et al. 260/606.5 P 3,681,281 8/1972 Juelke et al. zen/45.7 P

OTHER PUBLICATIONS Ishizuka et al., Chemical Abstracts, Vol. 9 (1973) No. 5457v.

Primary ExaminerArthur P. Demers Attorney, Agent, or FirmAnthony P. Mentis [57] ABSTRACT Aromatic phosphine oxide compounds are useful as flame retardants in synthetic polymers and textiles. Exemplary is 2,4,5,6-tetrabromo-l,3-xylylenebis(diphenylphosphine oxide).

10 Claims, No Drawings 1 PHOSPHINE OXIDE FLAME RETARDANTS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is concerned with new classes of phosphorus-containing compounds which are useful as flameretardants for polymers, and particularly for textiles.

2. Prior Art Kokai, Japanese 73 04, 451 to Asahi Denko Co., Chem. Abs. 79, 5457 v (1973), describes certain phosphine oxide compounds which are not the same as the instant compounds.

U.S. Pat. No. 3,370,030 discloses a flame-retardant composition comprising two critical components: a particular kind of phosphine oxide compound and a chlorinated hydrocarbon material such as chlorinated biphenyl.

US. Pat. No. 3,681,281 discloses a flame-retardant composition comprising a tertiary phosphine oxide such as xylylenebis(diphenylphosphine oxide).

DESCRIPTION OF THE INVENTION The new flame-retardant compounds have the for mulas R and R individually, are alkyl, aryl or aralkyl, each of up to carbon atoms having up to five chlorine, bromine or fluorine atoms;

X is chlorine, bromine, OR, SR, SOR, SO R, SO NH SO Nl-IR or SO NR R being as defined R and R are defined as above;

Y is alkyl of one to six carbons;

c is 0 to 3;

d is 3 to 6; and

c d is 3 to 6.

In the compounds of formula I, preferred flameretardant properties coupled with compatibility with the substrate and high temperature resistance are found in the compounds where at least one of R and R is phenyl, X is chlorine or bromine and a is 2 to 4. When X is other than halogen, a is generally 1 to 2.

The compounds of formula II which have the highest phosphorus content impart maximum flame-retardant properties for a minimum loading of the flameretardant agent in the polymer. A preferred group are the compounds in which 0 is O.

(III) b RR r-on a 0 7X II 1 2 (CH P-RR R z where Z is chlorine or bromine, R is alkyl of up to eight carbon atoms, and X, R, R, a and b are as previously indicated.

t agr s where all of the letters are as previously indicated.

The processes can be runwith' or without solvent.

Without solvent, the reactants can be mixed and then heated to reaction temperature or, alternatively, the

xylene, and toluene. 10

The reaction temperature ranges are 25-300C., with ll200C being preferred.

The reaction times range from about minutes to about 24 hours, with l to 5 hours being preferred.

The reactions are advantageously conducted in the substantial absence of air and moisture.

SPECIFIC EMBODIMENTS OF THE INVENTION The following are illustrative examples of the invention in which all parts are by weight and all temperatures are in degrees Centigrade unless otherwise stated.

EXAMPLE 1 2,4,5 ,6-Tetrabromo-l ,3-xylylenebis( diphenylphosphine Oxide) X Br; a 4; b

1 R R C H H Br 2(C H 2P-OCH3 ---7 Br r II B CH2P(C6HS)2 2CH B1 (CsHs gPCH Br To a stirred, refluxing mixture of 10.00 g of alpha, alpha',2,4,5,6-hexabromo-m-xylene in 100 ml of o dichlorobenzene under nitrogen was added dropwise a solution of 15.00 g of methyl diphenylphosphinite in 50 ml of o-dichlorobenzene. After the addition was complete, the mixture was refluxed for 5 hrs and cooled. The white solid was filtered, washed with benzene and hexane, and recrystallized from dimethylsulfoxide to give 7.36 g of 2,4,5,6-tetrabromo-l,3-xylylenebis (diphenylphosphine oxide) as white crystals, m.p. 25 l-254.

Anal. Calcd for C H Br O P C, 46.75; H, 2,94; P, 7.54. Found: C, 46.54; H, 3.11; P, 7.32.

EXAMPLE 2 2,5-Dibromo-l ,4-xyly|enebis(diphenylphosphine oxide) P-OCH II (C6H5)2PCH2 EXAMPLE 3 2,3 ,5 ,6-Tetrabr0mol ,4-xylylenebis( diphenylphosphine oxide) To a stirred, refluxing mixture of 10.00 g of alpha, a1- pha',2,3,5,6-hexachloro-p-xylene in 150 ml of o- "dichlorobenzene under nitrogen was added a solution i of 20.00 of meth 1 di hen 1 hos hinite in 50 ml of BrCH CHEBr 6 5 o-dichlorfbenzene Aft r' the Eiddit ion was complete, the mixture was refluxed for 5 hrs and cooled. The

white solid was filtered, washed with benzene and hex- Br Br ane, and recrystallized from 750 ml of odichlorobenzene to give 18.50 g of 2,3,5,6-tetrachloro- 1O 1,4-xylylenebis (diphenylphosphine oxide) as white crystals, m.p. 339341 dec. Br Br Anal. Calcd for C H Cl O P C, 59.65; H, 3.76; P, 9.62; C1, 22.01. Found: C, 59.86; H, 3.89; P, 9.67; Cl, 0 O 22.17.

II II (C H5) PCH CH P(C H5) EXAMPLE 5 2,4,5 ,6-Tetrachloro-1 ,3-xylylenebis(diphenylphosphine oxide) Br Br Br Br To a stirred, refluxing mixture of 20.00 g of alpha, alpha,2,3,5,6-hexabromo-p-xylene and 200 ml of 0- 1 1 dichlorobenzene under nitrogen was added dropwise a solution of 30.00 g of methyl diphenylphosphinite in 100 ml of o-dichlorobenzene. After the addition was complete, the mixture was refluxed for 3.5 hrs and cooled. The white crystals were filtered, washed with benzene and hexane, and recrystallized from 600 ml of o-dichlorobenzene to give 23.20 g of 2,3,5,6- C1CH Cl tetrabromo- 1 ,4-xylylenebis(diphenylphosphine oxide), 2 dec. 310 with melting at 325-326".

Anal. Calcd for C H Br O P C, 46.75; H, 2.94. C1 C1 Found: C, 46.92; H, 3.21. O I EXAMPLE 4 c1 CH P C H 4o 2 6 5 2 2,3 ,5 ,6-Tetrachloro-1 ,4-xylyleneb1s( diphenylphos- 0 phine oxide) I! X: (C H5) PCH Cl a=4 b=2 20H Cl 11:12 3

To a stirred, refluxing mixture of 20.00 g of alpha, al-

pha',2,4,5,6-hexachloro-m-xylene in 300 ml of 0- ClCH2 CHQCl 6 5 2 dichlorobenzene under nitrogen was added dropwise 40.00 g of methyl diphenylphosphinite. After the addition was complete, the mixture was refluxed 4 hrs and C1 C1 cooled. The white solid was filtered, washed with benzene and hexane, and recrystallized from 100 ml of chlorobenzene to give 16.78 g of 2,4,5,6-tetrachloroc1 c1 1,3-xylylenebis(diphenylphosphine oxide) as white crystals, m.p. 228231. 0 Anal. Calcd for C I-1 0 0 15: C, 59.65; H, 3.75.

Found: c, 59.49; H, 3.85. (C H)PCH CHP(CH) 5 2 2 2 6 5 2 The filtrate from the reaction mixture deposited I more product as the benzene and hexane washes were mixed with it. The white solid was filtered, washed with C1 C1 hexane, and recrystallized from 50 ml of chlorobenzene to give 6.81 g of additional product, m.p. 201130]. 228-231.

EXAMPLE 6 2-Methoxy-5-methylthio-l ,4-xylylenebis(diphenylphosphine oxide) To a stirred, refluxing mixture of 2.50 g of 2- methoxy-S-methylthio- 1 ,4-bis(chloromethy1 )benzene in 50 m1 of o-dichlorobenzene under nitrogen was added dropwise 6.00 g of n-butyl diphenylphosphinite.

After the addition was complete, the mixture was refluxed for 3 hrs and cooled. The white solid was filtered, washed with benzene and hexane, and dried at 150 and 0.1 mm to give 5.31 g of 2-methoxy-5- methylthio- 1 ,4-xyly1enebis( diphenylphosphine oxide), m.p. 286288.

Anal. Calcd for C H O P S: C, 70.09; H, 5.54. Found: C, 70.32; H, 5.69.

EXAMPLE 7 2-Methoxy-S-methylsulfonyl-1 ,4-xyly1enebis(diphenylphosphine oxide) X OCH SO CH b 2 R R1 CGHE,

OCH

O 0 II II (C 11 PCH CH P(C I'1 2 I CH To a stirred solution of 1.75 g of 2-methoxy-5- methylthio-l,4-xylylenebis (diphenylphosphine oxide) in 50 ml of acetic acid at was added dropwise 1.80 g of 30% hydrogen peroxide. After the addition was complete, the mixture was heated at 70 for 3 hrs and then stirred for 18 hrs at room temperature. Water was added and the mixture was cooled. The resulting white precipitate was filtered, washed with water, and recrystallized from 50 ml of chlorobenzene to give 0.92 g of 2-methoxy-5-methylsulfonyl-l ,4-xylylenebis (diphenylphosphine oxide) as white crystals, m.p. 285.0286.5.

Anal. Calcd for C H O P S: C, 66.44; H, 5.25. Found: C, 66.63; H, 5.50.

EXAMPLE 8 2,4,6-Trimethyl-mesitylylenetris(diphenylphosphine oxide) X CH3 a 3 b 3 R R C H CH Cl CH H3O 011 01 5(C H5 P-OCH3-+ (C H5) PCH CH3 ll H30 CH P(C H5) 2 ll (C H5) PCH CH3 H Cl 3 To a stirred, refluxing mixture of 5.00 g of 2,4,6- tris(chloromethyl)mesitylene in ml of 0- dichlorobenzene under nitrogen was added dropwise a solution of 17.00 g of methyl diphenylphosphinite in 50 ml of o-dichlorobenzene. After the addition was complete, the mixture was refluxed for 5 hrs and cooled. The white solid was filtered, washed with benzene and hexane, and dried at 150 and 0.1 mm for 18 hrs to give 12.50 g of 2,4,6-trimethyl-mesitylylene-tris (diphenylphosphine oxide), 275-278.

Anal. Calcd for C H O P C, 75.58; H, 5.95; P, 12.18. Found: C, 75.18; H, 5.94; P, 12.56.

Disubstituted phosphinites which can be used are commercially available or can be prepared by reacting a disubstituted phosphinous chloride with a hydroxy compound, R OH, in the presence of a tertiary amine such as pyridine or triethylamine according to the reaction:

where R, R and R are as previously stated. Thus, by use of known phosphinous chlorides in the above reaction, useful disubstituted phosphinites, RRPOR", are prepared and include those shown in Table I.

Additional halomethyl substituted aromatic compounds II which can be used include the benzenesulfonamides where X is -SO NH and which have two to four CH Hal groups attached to the benzenoid ring. These compounds may be prepared by using N- bromosuccinimide (NBS) as in the reaction:

SO NH Suitable starting methyl benzenesulfonamides, where b is 2-4, have been described. N,N-disubstituted benzenesulfonamides are also readily available, eg,

BI'CH2QSO2N(C2H5) 2 and Reaction of these latter compounds with RRPOR give new compounds of the invention:

9 Y --P--CH2 SOQN 8 l Other halomethylsubstituted aromatic compounds II which can be used include the aryl sulfones where X is -SO R. Illustrative of the preparation of these sulfones is the reaction of benzenesulfonyl chloride and mxylene in the presence of AlCl sHs 2 CH Cells-S0 CH BI Cell -S0 CH P(C H5)2 Still other halomethyl substituted aromatic compounds II which can be used include the aryl ethers and aryl thioethers where X is OR and SR, respectively.

They have the formulas:

Rog-(CH b and RS-@'(CH b These compounds are available by reaction of a polymethylbenzene halide with an alkali metal salt of a thiol, alcohol or phenol, e.g.,

(DMF dimethylformamide) and DMF CHgQBI' E-CsH 10K --9 These ethers and thioethers by bromination as described above give the bromomethyl derivatives which are reactive with alkyl disubstituted phosphinites to give corresponding arylene disubstituted phosphine oxides, such as,

[I II (0 115) PCH CH P( ems 2 n (C6H5)2PCH2 O-E-CsH Oxidation of the thio compounds gives sulfoxides. Sulfones can also be obtained by further oxidation.

Specific compounds included within the scope of this invention obtained from previously described reactants are:

CbHs S02 CH P(a-C QH1}2 OCHa 9 S? (C5H5)2PCH2 CH2P(C6H5)2 (3 c1 c1 0 ll (C H5CH PCH CH P(CH C H 0 Br 0 II I! (R-ClC6H4) (C2H5)PCH2 CH2P(C2H5) -cle n 0 .Br Br Br 0 ll The use of the new compounds of this invention as flame retardants for polyolefins has been demonstrated by following the Underwriters Laboratory procedure (UL-94) in the following manner: Commercial polypropylene (28 g) was fluxed on a two-roll mill (Junior Lab 3 inch X 8 inch rolls), 12 g of the flame-retardant additive was added to the resin band, and the mixture milled ca. 6 minutes, during which time five to ten cuts were made to enhance blending. The resin sheet was ground up in a Wiley mill. The resulting powder was molded into 5 inch X /2 inch inch flex bars using a laboratory scale injection mold.

The bars (five from each batch) were subjected to flammability testing. The bars were supported vertically. Each sample was ignited twice, and 1 for 10 seconds with a Bunsen burner. After each ignition, there was no continued burning, i.e., the polymer was self-extinguishing. Even though all dripped molten polymer to cotton batting 12 inches below, the sample in only one of a series of five (using the compound of 40 Example 4) did the cotton ignite. Compounds used in the test included those of Examples 1, 2, 4, and 8. In contrast to these results, when 1,2-xylylenebis- (diphenylphosphine oxide) was used in the same manner as a control, three of the five samples ignited the 45 cotton. The data are presented in Table II.

Table II Time Burn Time Burn Ignite of 1 Time of I Time Drip? cotton? 2 1222. 29 2212. 2 2;. sec 1. 15. Iss2). IEEJBBL 1 l0 l0 y 0 1- Br CH P(O) 2 l0 1O yes no s: @131 3 1o 10 y no CH 4 l0 l0 yes no Br 2 2 5 10 1o yes no 1 Br 1 1O l0 yes no 2 ll) 10 yes no 2 (0) 2 2 2 3 10 1o yes no Br 4 ll) 10 yes no 5 l0 l0 yes no C1 C1 4 l 10 1O yes yes P O CH 2 l0 l yes no 2 2 Z 2 3 l0 l0 yes no 4 1O 10 C1 C1 Y no 5 1O 10 yes no Time. Burn Time Burn Ignite of I Time of I Time Drip? cotton? Example Cogound No. (set) Z y ji /no) H C CH P(O)' 1 l0 1O yes no 2 I 10 l0 es no 2 2 3 3 1o 1o yes no Cl-l P(0)(Z 4 l0 l0 yes no 5 l0 l0 yes no l l0 yes yes gilt-12l- 2 (OM62 2 l0 10 yes yes 3 l0 1O yes no 2 (O) 2 4 l0 l0 yes no 5 10 1'0 yes yes In another test for flame retardancy, a mixture of l g of 2,5-dibromo-p-xylylenebis(diphenylphosphine oxide) and 9 g of powdered polyethylene terephthalate was dry-milled for 60 minutes. Two grams of the resulting mixed powder was pressed on a fiberglass cloth in a platen press at 280C to obtain a glass-supported film. The film was cut into five strips which were suspended horizontally and ignited with a wooden match. The first half inch of burning was ignored. All five samples selfextinguished in 5-10 seconds after burning less than A inch (about 0.025 in/sec). A control glass-supported polyethylene terephthalate film burned completely in 40 seconds (0.05 in/sec).

The compounds of this invention are also useful as flame retardants with many synthetic polymers including polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; and polyamides such as nylon 6. They are generally incorporated in polymers by melt blending but can be mixed in powder or liquid form. Surface treatment of textiles also provides fire-retardant properties. In general, amounts of 1-25% by weight of the new phosphine oxides are admixed with the polymer for improvement in fire-retardant propertiesv Preferred results are obtained when 5-15% of the phosphine oxide is used.

The fire-retardant or flame-retardant property of a material refers to its resistance to burning and its capacity to be self-extinguishing when once ignited. Preferred compositions containing the compounds of this invention are those which when ignited by a flame are self-extinguishing when the source of that flame is removed.

Textiles include particularly those fabrics formed from fibers by weaving, knitting or non-woven techniques.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A flame-retardant compound of the formula wherein R and R individually are alkyl, aryl or aralkyl each of up to 10 carbon atoms having up to five chlorine, bromine or fluorine atoms;

X is chlorine, bromine, OR, SR, SOR or SO R, R

being as defined above;

a is l to 4;

b is 2 to 5; and

a plus bis 3 to 6.

2. A compound of claim 1 in which at least one of R and R is phenyl, X is chlorine or bromine and a is 2 to 14.

3. A compound of claim 1 in which R R phenyl,

= 3 and b 3.

4. The compound of claim 2 in which X bromine and a 4; 2,4,5,6-tetrabromo-l,3-xylylenebis(diphenylphosphine oxide).

5. The compound of claim 2 in which X bromine and a 2; 2,5-dibromo-l,4-xylylenebis(diphenylphosphine oxide).

. 6. The compound of claim 2 in which X bromine and a 4; 2,3,5,6-tetrabromo-l,4-xylylenebis(diphenylphosphine oxide).

p ge 'I of 2 UNITED STATES PATENT OFFICE (IERTIFICATE OF CORRECTION group and a hyphen added to indicate that the rest of the formul on line 37 had been broken off.

Column 12, line 29, a hyphen should be added at the en Ff the line to indicate that the rest of the formula on line 34 had been broken off.

Column 12, line 55, "bromomethylbenzene" should be bromomethyl)benzene-.

Column '15, line 63, the formula is indistinct and does not appear to show the subscript "b" at the end of the line;

PATENT NO. 3,895,074

DATED July 15 1975 'NVENTOR(5) 3 Joseph J. Mrowca It is certified that error appears in the above-identified patent and that said Letters Patent Q are hereby corrected as shown below:

Column 3, line 35, "2(C H should be a Column 3 line 42 POCH should be canceled.

Column 9, line ll, "(C H PO-n-C H should be Column 9, line 17, "(pClC H (C H POC H should be (pClC H (C H )POC H 0 l Column 10, line 31, "P" should have been kept as the P Page 2 of 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 95 074 DATED July 15, 1975 INVENTOM5) Joseph J. Mrowca g It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

see column 1, line-27.

Column 16, line 33, "14" should be -4-.

T Signed and Sealed this thirtieth D a )1 f March 1976 [SEAL] Arrest: Q

RUTH. C. M AHSON C. MARSHALL DANN Alreslmg Officer (ummixsiuner ofParents and Trademarks 

1. A FLAME-RETARDANT COMPOUND OF THE FORMULA
 2. A compound of claim 1 in which at least one of R and R1 is phenyl, X is chlorine or bromine and a is 2 to l4.
 3. A compound of claim 1 in which R R1 phenyl, a 3 and b
 3. 4. The compound of claim 2 in which X bromine and a 4; 2,4, 5,6-tetrabromo-1,3-xylylenebis(diphenylphosphine oxide).
 5. The compound of claim 2 in which X bromine and a 2; 2,5-dibromo-1,4-xylylenebis(diphenylphosphine oxide).
 6. The compound of claim 2 in which X bromine and a 4; 2,3, 5,6-tetrabromo-1,4-xylylenebis(diphenylphosphine oxide).
 7. The compound of claim 2 in which X chlorine and a 4; 2, 3,5,6-tetrachloro-1,4-xylylenebis(diphenylphosphine oxide).
 8. The compound of claim 2 in which X chlorine and a 4; 2, 4,5,6-tetrachloro-1,3-xylylenebis(diphenylphosphine oxide).
 9. The compound of claim 1 in which X OCH3 and SCH3, a 2, b 2 and R R1 phenyl; 2-methoxy-5-methylthio-1,4-xylylenebis (diphenyl phosphine oxide).
 10. The compound of claim 1 in which X OCH3 and SO2CH3, a 2, b 2 and R R1 phenyl; 2-methoxy-5-methylsulfonyl-1,4-xylylenebis(diphenylphosphine oxide). 